`dspace-solr` Docker build fails due to multi-line ENV parse error

[MMilosz]

Describe the bug

The dspace-solr Dockerfile fails to build due to a parse error on multi-line ENV variables. Seen on main branch.

To Reproduce

1. Remove any existing image 4science/dspace-cris-solr
2. Run docker compose -f docker-compose.yml build --no-cache
3. Observe the following error:

Dockerfile:33

--------------------

  32 |         AUDIT_CONFIGSET_PATH=/opt/solr/server/solr/configsets/audit/conf

  33 | >>>     DEDUP_CONFIGSET_PATH=/opt/solr/server/solr/configsets/dedup/conf \

  34 | >>>     OCR_CONFIGSET_PATH=/opt/solr/server/solr/configsets/ocr/conf \

  35 | >>> 

  36 | >>> USER root

  37 |     

--------------------

target dspacesolr: failed to solve: dockerfile parse error on line 33: unknown instruction: DEDUP_CONFIGSET_PATH=/opt/solr/server/solr/configsets/dedup/conf

Expected behavior

Dockerfile should build succesfully with all Solr config paths set.

Related work

Fix proposed in PR #545